[SOLVED] How to read file from s3 with uproot?

How to read file from s3 with uproot?

Is there a way to open a ROOT file using s3?

ROOT support reading (but not writing) with TS3WebFile

Solution

Since uproots support http it is possible to convert s3 resource to http signing the URL. It can be done with boto3:

import boto3
s3_client = boto3.client('s3', endpoint_url=my_endpoint)
url = s3_client.generate_presigned_url('get_object', Params={'Bucket': my_bucket, 'Key': my_key}, ExpiresIn=10000)

f = uproot.open(url)

There are various authentication method using boto, e.g. via environment variables AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY.

The same procedure (thanks Chris) can be done without any special library, just implementing the algorithm provided by s3 (https://docs.aws.amazon.com/general/latest/gr/sigv4-signed-request-examples.html, http://awsdocs.s3.amazonaws.com/S3/latest/s3-qrc.pdf)